1. Field of the Invention
The present invention relates to a fore-and-aft suspension device for use in an automotive seat, which is designed to absorb a horizontal forward/backward load, impact or jolting applied to the seat in its longitudinal direction, as opposed to an ordinary vertically operable seat suspension device.
2. Description of the Prior Art
It has been known that a horizontal forward/backward load, impact or jolting applied to a seat during driving an automobile is absorbed by use of a fore-and-aft suspension device, in contrast to an ordinary seat suspension device for absorbing a vertically applied load or jolting. Among various hitherto such fore-and-aft suspension devices, the following two prior arts indicate a basic technical concept for absorbing a horizontal forward/backward load or jolting exerted on the seat: the Japanese Laid-Open Publication Nos. 54-125047 and 54-95406. According to them, there is basically disclosed a structure wherein a pair of spaced-apart coil spirngs are wound around a horizontal shaft, an upper bracket fixed to the seat, the upper bracket being fixed to both ends of the horizontal shaft, and at the midway point of the shaft, a shaft bearing member is provided such that the shaft is inserted through the shaft bearing member in a manner slidable therein in a a forward and backward direction, the shaft bearing member being fixed at the floor side. Thus, when a forward or backward jolting or load is applied to the seat, the upper bracket fixed thereto is slidable elastically on the shaft bearing member fixed at the floor side, whereupon the seat is slidable forwardly and backwardly relative to the floor, and due to the resiliency of the coil springs, the jolting or load is absorbed, to thereby reduce the forward and backward impact on an occupant on the seat.
However, the foregoing prior arts have been found not complete in designing to absorb any practical force components of such forward and backward jolting or load. In other words, they are merely constructed to absorb a straight forward and backward load, and in practical use, a straight forward and backward load is not always applied to the seat, and most frequently, the forward and backward load is applied from various angles to the seat, and therefore, the load is not applied in a direction coaxially of the foregoing horizontal shaft, but applied obliquely thereto. Consequently, the horizontal shaft is strongly abutted against the shaft bearing member, causing a great friction therebetween to prevent the sliding movement of the horizontal shaft, or deforming the horizontal shaft per se, resulting in no sliding action thereof within the shaft bearing member. As such, a sufficient absorption of the forward/backward load or jolting is in no way attained.